A laboratory incubation experiment was conducted to investigate the decomposition of maize straw incorporated into soil amended with nitrogen (N) and moisture (M) levels. Clay loam topsoil amended with maize straw was adjusted to four initial nitrogen treatments (C/N ratios of 72, 36, 18, and 9) and four moisture levels (60%, 70%, 80% and 90 % of field capacity) for the total of 16 treatments and incubated at 20°C for 51 days. CO2-C evolved was regularly recorded for all treatments during entire incubation period. Results showed that the mixing of straw with soil accelerated decomposition rates and enhanced cumulative CO2-C production. The incorporation of straw brought about 50% increase in the cumulative CO2-C production as compared with controls. About 45% of added maize straw C was mineralized to CO2-C in 51 days. We conclude that incorporation of straw into soil along with the addition of N and moisture levels significantly affected CO2-C evolution, cumulative CO2-C, C mineralization and soil organic carbon deposition. The CO2 emission was in positive correlation with (R2=0.99) N, moisture and incubation time (days). The straw returning into soil may enhance carbon pools and, thus will improve soil and environmental quality.